1. Field of the Invention
This invention relates to an electrical apparatus of the type suitable for programming electrical circuits by selectively severing fusible means in the electrical apparatus, and more particularly this invention relates to an electrical connector or electrical component having a plurality of signal terminals which are initially attached to ground by a fusible member, the connections between individual signal terminals and ground being selectively severable upon the application of an electrical current. Furthermore, this invention relates to a connector apparatus which can be reprogrammed by electrically severing each connection from a signal terminal to ground, and attachment of an auxiliary device, itself programmed to establish electrical paths between signal and ground terminals so that the connector can be reprogrammed.
2. Description of the Prior Art
It is quite common to use subassemblies employing electronic means which are often manufactured in a configuration which is suitable for use in a number of related but different ways. The electronic components used in the standard assemblies can then be programmed for use in specific devices. For example, the same electronic subassembly could be used for a number of different sizes of the same device, but the electronic components comprising a portion of this subassembly would need to be separately programmed for each size.
One example in which such electronic subassemblies have been employed would be in electronic odometers used in automobiles. In order to achieve the economic benefits from mass production of such subassemblies, a single standard electronic subassembly might be manufactured and then programmed for use in different size automobiles. A prior art example of an electronic subassembly 2' used on an electronic odometer is shown in FIG. 1. This subassembly employs an integrated circuit component such as a dual inline package 4 to provide the logic for the odometer. The dual inline package 4 is mounted on a printed circuit board 6. A plurality of pins in the dual inline package 4 are connected to a plurality of individual traces 8 which are, in turn, initially commoned to ground. Each trace 8 has a discrete fuse 16 located between the dual inline package 4 and ground and, upon the application of an electric potential sufficient to induce a current through the individual trace 8 in excess of the current capacity of the corresponding fuse 16, that fuse will be blown or severed thus interrupting the connection between the corresponding pin and ground. In this manner, the integrated circuit component 4 can be electronically programmed for a specific use, for example for a specific automobile tire size.
The prior art subassembly 2', shown in FIG. 1, can also be mechanically reprogrammed in the event of a subsequent change in the vehicle, for example installation of a different size tire. The electrical connector 18 and the pin header 10 can be used to mechanically reprogram the subassembly 2'. In practice, a header 10, having a plurality of pins 12 attached to a ground bus 14, would be inserted into the connector establishing interconnection to the terminals in the prior art connector 18. Electrical potential could then be applied to the bus 14, thus blowing all of the remaining fuses 16 between the prior art connector 18 and ground. The pin header 10 can then be removed, and selected pins 12 can be removed from the ground bus 14. When the pin header 10 is then re-inserted in the connector 18 and the ground bus 14 is connected to ground, the pins remaining in the mechanically programmed pin header 10 will form an interconnection between the corresponding lead of the dual inline package 4 and ground. Note that the terminals in connector 10 do not interrupt the traces between the leads on the dual inline package 4 and ground.
Although this prior art subassembly does provide for both electrical and mechanical programming of an integrated circuit component, the device does have certain disadvantages. First, the device requires a number of discrete components, including the separate fuses and the connector. These separate components not only provide logistical problems, but also take up valuable space on a printed circuit board. Furthermore, it is difficult to control the precise current carrying capacity of conventional discrete fuses, and such a manufacturing variability can result in use of the wrong size fuse.
Other standard components which can be used to program an electric circuit of this type can comprise a conventional DIP switch in which individually actuatable switches can be used to program and reprogram an integrated circuit component such as a dual inline package. Although such devices provide virtually unlimited reprogramming capability, DIP switches are relatively expensive and must be mechanically accessible, and thus can add significant cost to mass produced items.
The instant invention comprises an electrical connector which can be both mechanically and electrically reprogrammed and thus would be suitable for use in a number of applications in which the device would be programmed only a limited number of times during its life.